Pex13 encodes an SH3-containing peroxisomal membrane protein required for the import of proteins into peroxisomes. PEX13 is an integral membrane protein on the peroxisome that regulates peroxisomal matrix protein import during peroxisome biogenesis. PEX13 spans approximately 11 kb on chromosome 2 and contains four exons, one more than previously thought. The corrected PEX13 cDNA is predicted to encode a protein product with a molecular mass of 44,312 Da. Mutations in PEX13 and other peroxin proteins are associated with Zellweger syndrome spectrum (ZSS) disorders, a subtype of peroxisome biogenesis disorder characterized by prominent neurological, hepatic, and renal abnormalities leading to neonatal death. In humans, mutations in PEX13 can disrupt peroxisome biogenesis and lead to peroxisomal metabolic dysfunction and neurodegenerative disease.